JPS6351628B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a public telephone set that prevents coins from jamming due to a full safe.

Conventionally, public telephones have been proposed that accumulate information on coins stored in a safe and store it in memory, and when the accumulated value reaches a predetermined value, prevent future paid calls from being made to prevent coin jams due to the safe being full. ing.

Therefore, in the above-mentioned public telephone,
When the safe is replaced, it is necessary to clear the accumulated coin information to zero. On the other hand, in public telephones powered by a central office, the exchange is not activated when on-hook, and the current that can be supplied from the exchange to the public telephone is extremely small, enough to back up the memory. The device could only operate when off-hook.

However, in the above-mentioned public telephone,
When a safe is exchanged during an on-hook period when the control circuit is not operating, a problem arises in that the coin information stored in the memory is not cleared to zero. For this reason, the next time you go off-hook and start a call, the coin information will continue to be accumulated, and when the accumulated value reaches a predetermined value, it will be determined that the safe is full, even though the safe is not actually full. However, it had the disadvantage that subsequent paid calls would be prohibited.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a public telephone that can reliably clear coin information stored in a memory to zero when a safe is replaced.

In order to achieve this purpose, the public telephone of the present invention uses a holding circuit to maintain that the safe contact has operated when the safe is removed, and when the first off-hook operation after replacing the safe is performed, the holding circuit outputs If there is, the coin information will be cleared to zero. The present invention will be described in detail below using drawings showing examples.

The figure is a block diagram showing one embodiment of a public telephone according to the present invention. In the figure, a billing signal receiving circuit 1, a diode bridge 2, a dial impulse sending and forced disconnection circuit 3, a power supply circuit 4, a dial shunt circuit 5, a telephone communication circuit 6, a control circuit 7, a telephone switch HS, and a central office line terminal _L1. , L ₂ constitutes a public telephone circuit. In addition, 8 is a holding circuit, 9
is a safe contact, and the holding circuit 8 maintains that the safe contact 9 has operated.

Furthermore, the power supply circuit 4 is composed of a high resistance 41, diodes 42 to 46, capacitors 47 to 50, and a Zener diode 51. Only the capacitor 50 is trickle charged through the high resistance 41 during on-hook, and during off-hook, capacitor 4
7 to 50 are charged by the communication current.

The safe contact 9 is turned on when the safe is pulled out, and the holding circuit 8 that maintains that the safe contact 9 is activated includes a pull-up resistor 81, a chattering prevention circuit 82, a flip-flop 83, and a resistor 84. , 85.

Further, the control circuit 7 is a central processing unit (hereinafter referred to as
It consists of a read-only memory (hereinafter referred to as ROM) 72, and a random access memory (hereinafter referred to as RAM) 73, and according to the program written in the ROM 72,
The CPU 71 performs necessary control, and coin information generated in a coin storage circuit (not shown) is stored in the RAM 73.

Note that the power supply voltage for the holding circuit 8 and the RAM 73 is supplied by the capacitor 50 regardless of on-hook or off-hook, and the power supply voltage for the CPU 71 and the ROM 73 is
The power supply voltage 72 is supplied only during off-hook.

In addition, the ROM 72 is written with a program for the control operation performed by the CPU 71 after off-hook.
As the first operation after off-hook, the holding circuit 8
monitors the output, and when there is an output, RAM73
This program controls the coin information stored in the coin information to be cleared to zero.

The operation of the public telephone set as described above is as follows. When a safe is replaced while on-hook to retrieve the coins contained in the safe, the safe contact 9 is activated and this information is supplied to the holding circuit 8. Since the holding circuit 8 is supplied with the power supply voltage regardless of whether it is on-hook or off-hook as described above, the chattering prevention circuit 8
A flip-flop 83 connected to the safe contact 8 via a resistor 85 retains this information whenever the safe contact 7 is activated and transfers it to the CPU 71 via a resistor 85.
is supplied to the input terminal 71a of.

After that, when an off-hook operation occurs, the CPU
71 monitors the state of the input terminal 71a according to the program written in the ROM 72, but when the safe contact operates during on-hook, the holding output of the holding circuit 8 is supplied to this input terminal 71a. Therefore, according to this condition, CPU 71 uses RAM 73
The coin information stored in the coin information is cleared to zero, and then a reset signal is sent from the output terminal 71b to reset the flip-flop 83.

In this way, the operation of the safe contact 9 is on-hook,
Since the holding circuit 8 holds the safe regardless of the off-hook, there is no need for any conventional operations associated with replacing the safe, such as off-hook. Further, even if the safe is exchanged after an off-hook as is conventionally done, the coin information in the RAM 73 is cleared to zero by the first off-hook operation after the safe is exchanged.

Note that although the above embodiments have been described for public telephones using central power, commercial power supply public telephones also require off-hook control circuits, especially CPUs.
can be similarly applied to anything that works.

As explained above, the public telephone according to the present invention monitors the holding output outputted from the holding circuit when the safe is exchanged during off-hook, and when there is a holding output, the coin information is set to zero by the control circuit. Since the coin information is cleared, the coin information can be cleared to zero by simply replacing the safe, and this prevents paid calls from being made even though the safe is not full, which occurs due to malfunctions when replacing the safe. It has the effect of preventing call failures, and is particularly suitable for use in stored program type public telephones.

[Brief explanation of the drawing]

The figure is a block diagram showing one embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Billing signal receiving circuit, 2... Diode bridge, 3... Dial impulse sending and forced disconnection circuit, 4... Power supply circuit, 5... Dial shunt circuit, 6... Call circuit, 7... Control circuit,
8...Holding circuit, 9...Safe contact.

Claims (1)

[Claims] 1. In a public telephone whose control circuit starts operating when off-hook and stores information on coins stored in the safe in its memory, there is a safe contact that operates when the safe is removed, and a holding circuit that maintains that the safe contact has operated. A public telephone set comprising: the control circuit monitoring the output of the holding circuit during off-hook, and clearing the coin information stored in the memory when the output is present.